The overall goal of the research project it to develop a profile of enzyme tests that will be useful for following the clinical course of cancer patients in the manner that other biologic markers such as HCG or CEA, are currently being used. Results to date indicate that enzyme changes occur within one week of administration of chemotherapeutic agents that would appear to be useful in predicting response. Our current effort is directed at selecting a group of such tests that can most practically be run on serum samples of cancer patients. Meanwhile, we are accumulating data, which, when subjected to computer analysis will determine the usefulness of each such test for the proposed purpose and will select the best group of tests for increasing the probability of accurate predictions. Three groups of patients are being studied. All of which have had documented malignant disease. 1. Patients clinically free of disease but with a high risk of recurrence. 2. Patients with measurable or residual disease about to embark on a new treatment regimen. 3. Patients susceptable to the development of brain metastases. Groups 1 and 3 are being studied for recurrence of disease by measurements on serum and CSF respectively. Group 2 is being studied for response to therapy.